sfc: Explicitly prefetch RX hash prefix, not just Ethernet heade

Currently we prefetch from the Ethernet header, but we will also read
the hash prefix.  In practice they should be in the same cache line
and this won't hurt, but it is still pointless to add on the hash
prefix size.
Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>

drivers/net/ethernet/sfc/rx.c

@@ -458,7 +458,7 @@ void efx_rx_packet(struct efx_rx_queue *rx_queue, unsigned int index,
 	/* Prefetch nice and early so data will (hopefully) be in cache by
 	 * the time we look at it.
 	 */
-	prefetch(efx_rx_buf_va(rx_buf) + efx->type->rx_buffer_hash_size);
+	prefetch(efx_rx_buf_va(rx_buf));
 
 	/* Pipeline receives so that we give time for packet headers to be
 	 * prefetched into cache.